A 17-year-old boy is dead and an 18-year-old man is in custody today after a stabbing in Walnut Creek late Wednesday night, Walnut Creek police Lt. Mark Covington said.The Police Department received a call from Kaiser Hospital’s emergency room shortly after midnight Wednesday reporting that the victim’s friends had brought him to the hospital with multiple stab wounds. He died from his injuries at the hospital, Covington said.The Contra Costa County coroner’s office identified the victim today as Rodeo resident Jonart Yambao. Investigators determined that Yambao had been assaulted outside on Clover Lane near Nicholson Road. They later arrested Daniel Avanesyan on suspicion of murder, Covington said.Police were not releasing any information today about what led up to the stabbing or whether the victim knew Avanesyan.